feat: organize the session library

[wolfiesch]

What changed

• add folder and flat session-library layouts with Priority, Last updated, and Manual order
• add search, status filters, pinned folder/session shortcuts, and bounded Show more rendering
• persist organization, sorting, pins, and manual order while resetting transient filters on restart
• document the workflow and cover filtering, priority, persistence, sanitization, and manual movement
• refresh the required provenance checksums for the two changed session UI source files

Verification

• pnpm check
• pnpm test (all packages; web: 989 tests)
• pnpm build:web
• pnpm build:site
• desktop and 390x844 browser review; no console warnings/errors

[chatgpt-codex-connector]

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[Copilot]

Pull request overview

This PR reorganizes the web app’s session rail into more scalable “session library” layouts by adding organization modes (by-folder vs flat), new filtering/search affordances, pinning, and manual ordering, with persistence/sanitization in the workspace store and updated tests/docs.

Changes:

• Add rail organization/sort/filter/search + pinned shortcuts + bounded “Show more” rendering in the session rail UI.
• Extend session grouping logic to support priority sorting, manual ordering, flattening, and filtering/query matching.
• Persist new rail preferences (organization, sort, pins, manual order) while keeping query/filter ephemeral; update tests and docs accordingly.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
FEATURE_MATRIX.md	Updates capability matrix entry to reflect the new session-rail organization/sort/filter/pinning behavior.
apps/web/test/workspace-store.test.ts	Adds persistence and pin/manual-order coverage; confirms query/filter are not persisted.
apps/web/test/session-tree.test.ts	Adds tests for rail filtering, priority sort, manual ordering, flattening, and movement logic.
apps/web/src/state/workspace-store.ts	Introduces new persisted rail fields, sanitization helpers, and bumps workspace state version.
apps/web/src/lib/session-tree.ts	Implements rail filter/query matching, priority/manual/updated sorting, flattening, and manual reordering helper.
apps/web/src/components/Rail.tsx	Implements the new rail UI: options menu, search, filters, pinned section, flat layout, and bounded rendering.
apps/web/src/components/AppShell.tsx	Wires rail options into group-building and ensures unfiltered current groups are used where needed (collapsed rail, palette, pinned source).
apps/site/src/docs/content.ts	Documents the new organization/sort/filter/pin/manual-order workflow and persistence semantics.

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